Word about her classes quickly spread and two years later, overwhelmed by the demand, Khalifeh opened the country's first women-only martial arts center.
At the facility in north Amman, her young students throw fast punches, closely following instructions from their short-haired, 31-year-old coach.
"My aim is to empower women and to make them confident and able to defend themselves," said the taekwondo athlete who won a gold medal at the 2003 Junior Asian Championships.
"Sexual harassment happens worldwide. It's not as bad in Jordan as in Egypt for example, but it does exist -- especially on public transport and in some neighbourhoods of Amman."
Since starting SheFighter, Khalifeh says she has trained some 14,000 women and girls aged between four and 75 -- including thousands of Syrian refugees and foreign domestic workers through NGOs.
In May last year, she was invited to the White House in Washington as one of several inspiring young entrepreneurs from around the world.
"We want to empower leaders of social change like Lina Khalifeh of Jordan," US President Barack Obama said in his speech, singling her out.
- More protection needed -"Women have to be able to defend themselves" since Jordanian law does not provide women with enough protection from harassment, rape or domestic violence, she said.
Over the past few years, rights groups have increasingly denounced violence against women in Jordan and demanded legal amendments to better protect its victims.
The country's penal code allows a rapist to avoid prison if he marries his victim.
And while murder is punishable by the death penalty, in so-called "honour killings" -- the murder of a female relative believed to have "dishonoured" the family -- courts usually commute or reduce sentences.
Khalifeh said that some people in the conservative kingdom had opposed her project, but that overall she had received "quite a lot of support".
"Some women who have signed up for classes at the centre have been the victims of violence, harassment -- even rape," she said.
One of her students, 18-year-old Farah Murad, said she joined the classes after a young man harassed her in the street.
"It happened in broad daylight," she said. "I was walking down the street when this guy caught me by the shoulder. I pushed him back but then I didn't know what to do, so I ran all the way home."
But classes at SheFighter have helped.
- 'Head held high' -"I'm no longer scared," Murad said. "Now I walk in the street with my head held high during the day and after dark. I know how to defend myself."
In two- to three-month courses for four levels, Khalifeh teaches a mixture of taekwondo and boxing, as well as self-defence tricks like how to escape a strangling hold or hair grab.
Taekwondo, originally developed in Korea more than 2,000 years ago as a form of self-defence, involves using bare hands and feet to repel an opponent, often with trademark spectacular kicks.
Lujein Darwish, 16, said she fended off a harasser using skills she learnt over six months at the martial arts centre.
"Women need to be strong to defend themselves in these situations, especially when they're alone in the street," she said.
And then there are those who attend SheFighter's two- to three-month classes for sport.
"I've been doing taekwondo since I was a child because I love it," Rouba Massaada, 17, said.
"But, of course, if someone harasses me or says something hurtful, they should watch out," she added, smiling. - AFP